[DependencyInjection] fixed #8570
[DependencyInjection] fixed regression where setting a service to null did not trigger a re-creation of the service when getting it
merged branch fabpot/null-services (PR #8582)

This PR was merged into the 2.3 branch.

Discussion
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[DependencyInjection] fixed regression where setting a service to null did not trigger a re-creation of the service when getting it (closes #8392)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8392
| License       | MIT
| Doc PR        | n/a

Commits
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50d0727 [DependencyInjection] fixed regression where setting a service to null did not trigger a re-creation of the service when getting it
merged branch bronze1man/PR-setLazy-parent-2.3 (PR #8573)

This PR was merged into the 2.3 branch.

Discussion
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[DependencyInjection] setLazy not work on DefinitionDecorator

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8570
| License       | MIT
| Doc PR        | n/a

Commits
-------

970ce2c [DependencyInjection] fixed #8570
Merge branch '2.3'

* 2.3:
  [Form] fixes empty file-inputs get treated as extra field
  return 0 if there is no valid data
  [DependencyInjection] fixed regression where setting a service to null did not trigger a re-creation of the service when getting it
  [DependencyInjection] fixed #8570
  fixed file permission
  The ignoreAttributes itself should be ignored, too.
  [Tests] Tests on php 5.5 should pass
  [Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #88546)